<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    // var a = 3;
    // alert(a);
    // var a = "sadas";
    // alert(a);


    var num= 1;
    var num2 = 1.2;
    var num3 = NaN;

    //输出到页面上，类似sout
    document.write(num+"<br>");
    document.write(num2);
    document.write(num3);
    document.write(num,"<br>"+num2,num3)
</script>
</body>
</html>